Back when women weren't allowed to vote trans-identifying males would've still been able to - because voting eligibility was determined by sex, not "gender identity". So while they could've supported women's right to vote, like any male could, they wouldn't have been an actual part of the struggle.
Then let's look at today's times - currently there's the struggle to protect girl's and women's sports from males being permitted to compete in them and the struggle to be able to have some spaces designated only for us females. And they definitely can't be included in these struggles.
You can put a man in a skirt, make him grow his hair out, add heels and make up, heck! add boobs as well
But you can never take away the male energy, the male deportment,personality, interests, communication style behind those boobs.